1. Field of the Invention
This invention relates generally to an absorbent article, and more particularly to improvements in scrim reinforced absorbent cores having reduced stiffness. The reinforced absorbent structure can be employed in absorbent articles, such as disposable diapers, child's training pants, feminine care articles, incontinence articles, bandages, and the like.
2. Description of the Prior Art
Absorbent articles typically include fluid absorbent structures or cores conventionally formed by air forming or air laying techniques, and are placed between an intake function liner and a barrier function liner. The manufacture of the absorbent core may begin by fiberizing a sheet of cellulosic or other suitable absorbent material in a conventional fiberizer, or other shredding device, to form discrete fibers, and particles of superabsorbent material may be mixed with the discrete fibers. The fibers and superabsorbent particles are then entrained in an air stream and directed to and deposited on a foraminous forming surface to form an absorbent fibrous web. In addition, bonding agents or other strengthening components may be incorporated to provide a more stabilized web.
Other techniques have also been employed to form webs of stabilized absorbent material. Such techniques have included dry-forming techniques, foam-forming techniques, and various wet-laying and wet-forming techniques. The resulting webs of absorbent material have included absorbent fibers, natural fibers, synthetic fibers, superabsorbent materials, binders, and strengthening components in desired combinations. However formed, the absorbent web is then processed (e.g., cut into individual article cores) and assembled with other components (intake and barrier layers) to produce a final absorbent article. Absorbent material webs have also been strengthened by adding reinforcing members to the absorbent material webs. Such reinforcing members have included reinforcement filaments, tissue layers, fabric layers and netting materials. It is also known to add staple binder fibers to the absorbent materials upon formation of the absorbent material web. The binder fibers are activated by heat to produce adhesion of the absorbent materials.
Integrity of an absorbent core formed from such an absorbent material web is desirable to avoid bunching, clumping, cracking and separating of the absorbent core in either a wet or a dry state so as to improve the fit and comfort to the wearer of the absorbent article. Sagging and drooping of the absorbent article due to fluid insults can cause gaps between the article and the wearer's body which may lead to leaking, and poor integrity resulting in absorbent cracking and separating in use continues to be a common problem with conventional airformed absorbent cores.
As absorbent cores are made both thinner and narrower to achieve increased comfort (particularly in the crotch region), web stresses encountered in manufacture and use can be high, requiring better reinforcement. For instance, in manufacture tension on the absorbent core can be particularly high during start up and shut down of processing machinery. In use, the lack of integrity can make the absorbent article fit poorly and impact product performance through the cracking or breaking up of the absorbent core, and thereby inhibiting fluid control, liquid handling and wicking which can contribute to leaking.
Co-assigned European Patent Publication No. 0 467 409 A1 discloses one attempt to reinforce an absorbent pad using a scrim material. In that disclosure, a netting of scrim material is used in which some strands have an inner core of one material and an outer sheath of a second material having a lower melting point. The scrim is incorporated into a fibrous matrix, and this absorbent web is heated to melt the outer sheath for bonding the scrim to the matrix fibers. This requires an extra step in the manufacture of a reinforced absorbent.
European Publication No. 0 467 409 also discloses a method for establishing the position of the scrim within the body thickness of fibrous matrix. The method does not require a scrim of different materials, or suggest that the scrim can be secured without the use of adhesive and/or fusion bonding.
The incorporation of a scrim reinforcement material internally into the structure of the absorbent core dramatically reduces this integrity problem. However, in some cases certain scrim reinforcement can also result in undesirable absorbent stiffness which adversely impacts conformability, fit and comfort, especially in the crotch region of the absorbent article. The marginal edges of the scrim may cause skin irritation. These problems are particularly relevant for a narrow crotch geometry, where the buckling span is shorter as compared to wide crotch executions.
As a result, it has been difficult to achieve an absorbent structure having the desired features of low-cost, high strength and low irritation in addition to the basic attributes of comfort and high fluid absorption.